Conditioning the Competition Horseby Diederick Labuschagne

As the workload for competition horses increase so does the energy demand. Energy is the fuel needed to maintain all body functions and activity.

Energy is an important element of the diet but, fundamentally it is not a nutrient in the true sense. It is rather a collective element derived from various nutrients that maintains all biological processes and creates the capacity to work.

There is one and only one energy source that can fuel any process or activity in the body, Adenosine Tri Phosphate (ATP) which operates at cell level. Regardless of the source of energy consumed, be it carbohydrates, lipids (fat) or fibre, it has to be converted to ATP before it can be utilized. Very little ATP is stored in the body cells and readily available. It needs to be replenished on an ongoing basis. There are three energy pathways that keep this system intact. These are complex micro biological processes that all operate simultaneously at different modes and efficiencies. The predominant pathway will depend on the kind and intensity of exercise executed at the time. However, for now we will focus on the macro elements of energy.​The basic measurement of energy is calories or Joules. One calorie is equivalent to 4,184 Joules. The energy content of feed stuffs and feed is normally expressed as kilocalories (kcal) or mega joules (MJ) per kilogram.​Energy can be measured at various stages of digestion and metabolism. Many models and systems have been developed to partition energy at different stages. The diagram below depicts the basic partitioning of energy.

Gross Energy.GE is the total heat generated from the complete combustion of all nutrients in a bomb calorimeter. It is the maximum amount of energy that can be derived from a nutrient and is also referred to as IE (intake energy), i.e. the total energy that the animal consumes. The availability of GE to the animal depends on the digestibility of the various nutrients.

Digestible Energy.DE is the energy available to the animal after the food has been digested and the waste products has been excreted in the faeces. DE is then GE less energy lost in the faeces.

Metabolizable Energy.ME is the energy available to the animal after the metabolic processes have been completed. The waste products of these processes are excreted via urine and gas release. ME is then DE less the energy lost in urine and gas. The first available ME will always be used to sustain vital basic functions (heat increment, basal metabolism and voluntary activity).​Net Energy.NE is the energy available to the animal for other functions such as reproduction, lactation, growth and work, after the vital basic functions have been fuelled.

There are two major feed stuff sources from which energy can be derived. These are carbohydrates and fats.

Carbohydrates:

Carbohydrates are classified in two groups. Non Structural Carbohydrates (NSC) which basically comprises of Starch and Sugar, and Structural Carbohydrates which are basically the different components of Fibre.

​Fibre:

Fibre consists of Hemicellulose, Cellulose and Lignin, which basically makes up the cell walls. Of these Hemicellulose is the most digestible, followed by Cellulose with Lignin the least digestible. ADF and NDF are indicators of this digestibility. Fibre is digested in the hind gut through bacterial fermentation. The by-product of this fermentation process is Volatile Fatty Acids (VFA) that is utilized as an energy source. If good quality roughage is supplied at the equivalent of 1,5% of the animals body weight on a daily basis this will ensure that the microbe population in the hind gut remains intact, control the pH at 7 and ensure the integrity of the gut resulting in the constant release of VFA. This constant supply of energy (24/7) is often overlooked and under estimated. A healthy hind gut also retains moisture preventing dehydration.Non Structural Carbohydrates:

NSC consists of Starch and Sugar. These are normally abundant in grains such as Maize, Oats, Barley and Wheat and, some of their by-products. However, it is worth noting that lush pastures can contain relatively high sugar content and must be utilized with caution. NSC are digested in the Fore Gut which is an acidic environment where enzymes are active. The by-product of this process is Glycogen which is absorbed and stored in the liver and muscles. Glycogen is the primary energy source for high intensity anaerobic (where no oxygen is involved) work for short periods.

It is important to note that the retention time in this portion of the gut is only 1,5 hours during which time all the ingested NSC needs to be digested. Any excess will flow through to the hind gut causing a proliferation of the fermentation process causing the formation of gas and lowering of the pH that could result in colic.

The rule of thumb to avoid these complications is to never feed more than 800 – 1000 grams of NSC in a single feeding.

Fats and Oils:

Fat and Oils are found in a variety of plant seeds. These seeds can be used as such (some need to be processed) or the Oil is extracted from the seed and added as a pure fat. Vegetable Oils are widely used in horse feed and once the animals have adapted to it they can digest fairly large quantities of it. Fats have the most concentrated calorific value of all feed stuffs and can be successfully used to formulate energy dense diets. The higher the omega 3 and 6 content the better the quality is deemed. Once digested the fat is stored in so called adipose or fatty tissue. These are long term energy stores and are not released as quickly as the glycogen stores. Utilization of fat tissue normally comes into play with prolonged work where aerobic (lung function and oxygen) processes are involved.Putting together the feed program:

Ultimately the feed program must support and sustain the horse’s ability to compete in a particular activity or discipline.Energy from Fibre is not negotiable and should always be given priority. This is an ongoing process and will supply the bulk of the energy needed for maintenance, whilst also ensuring optimal gut function.

The additional energy required will be determined by the intensity and duration of the activity. You will always require a combination of anaerobic (intense activity) energy and aerobic (prolonged activity) energy. The art is getting the ratio correct for the specific discipline and level that you compete at. Commercial nutritionist endeavour to address this by designing different products for different disciplines. For example a feed formulated for Endurance would be vastly different to that designed for Polo.

Needless to say, as much as your horse needs to be nourished correctly the correct exercise and training program also needs to be in place for success.

Lastly, the question may well be posed “how do I know my horse is getting the correct energy?” The simple answer to this is the condition of your horse. If the body score is too low you need more energy, if the body score is too high you need less energy.​Until next time happy riding!